Method of tracing the flow of water



ETHYLENEDIAMINE TETRAACETIC ACID (PARTS PER MILLION) Jan. 13, 1959' w.J. FRANK 2,868,625 METHOD OF TRACING THE FLOW OF WATER Filed July 22,1955 C-ALIBRATION CURVE FOR DETERMINATION F ETHYLENEDIAMINE TETRAACETICACID BY I THE NICKEL DITHIO- OXALATE METHOD 0 2o 40 so so I00 I I I ICOLORIMETER READING (CHART DIVISIONS) INVENTOR. WALLACE J. FRANK,

United States Patent METHOD OF TRACING THE FLOW OF WATER Wallace J.Frank, Houston, Tex., assignor, by mesne assignments, to JerseyProduction Research Company, Tulsa, Okla., a corporation of DelawareApplication July 22, 1955, Serial No. 523,944

7 Claims. (Cl. 23-230) The present invention relates to tracing the flowof waters. More particularly, the present invention is directed totracing the flow of water during its passage underground from a firstpoint to a second point. In its more specific aspects, the invention isdirected to tracing the flow of water used in water flooding operationsin oil and gas fields from which hydrocarbons are produced.

For the last 25 years, many chemicals have been used as a tracer inwater, in water production, and in water flooding in oil and gas fields.Tracers have also been used in detecting the flow of water in oil andgas wells, particularly where leakages may occur through a casing oraround a packer. Inorganic chemicals have been used in many instances totrace flow of water in wells and particularly water movement between awell drilled to kill a blowout and the blowout well. The inorganicchemicals used heretofore have been objectionable because of thedifliculty in detecting small concentrations particularly in cases whereparticular materials may be native to the water being traced. In manyinstances, inorganic chemicals have been naturally occurring andfrequently obscured the arrival of the water containing the traceinorganic compounds.

Organic materials have been inefiective because they are readilyadsorbed by argillaceous and other materials in the earth formationthrough which the water flows or with which the water comes intocontact.

It has now been discovered that ethylene-diamine tetra acetic acid andits water soluble salts, such as sodium, potassium, and lithium salts aswell as the calcium, magnesium, barium, strontium, nickel, copper,-iron,lead, cadmium, zinc, cobalt, aluminum, chromium and the like, salts, maybe added to the water, the flow of which is bc-. ing traced either in astream or througha pipe line, an oil or gas well conduit, or through anunderground formation. When a salt is used the sodium salt is preferred.Ethylene-diamine tetra acetic acid is available on the market and isknown to the trade as Versene or Tetrine. The Versenes are availablefrom the Bersworth Chemical Co., Framingham, Massachusetts. The compoundmay be added as a liquid or as a solid directly .to the water, the flowof which is to be determined.

The amount of the ethylenediamine tetra acetic acid or its water solublesalts may be as little as 1 part per million in the water but usually anamount sufficient to provide parts per million may be desirable. Higherconcentrations up to 50 parts per million may be used but ordinarily itwill be desirable to employ an amount in the range from about 3 to about15 parts per million; at the lower concentrations, the detection of thewater is quantitative whereas in concentrations of at least 5 parts permillion the detection is qualitative. The invention may thereafter beused for both the determination of qualitative and quantitative flow.The arrival of the water from a first point to a second point remotefrom the other methods of tests may readily be used. In a test water,such as salt water containing ethylenediamine tetra acetic acid or thesodium salt thereof, which is preferred, the water may be flowed from afirst point to a second point remote from the first point, samples ofabout 200 cc. of the water containing the compound may be demineralizedby passing same through an anion-cation demineralizer to remove anynaturally containing salts, if desired. Passage of the salt watercontaining the ethylenediamine tetra acetic acid or its salt has nodetectable effect on the concentration of the ethylenediamine tetraacetic acid in the water. 100 cc. of the demineralized water is thenadjusted to a pH of about 6.5 to which is added approximately 5 cc. ofammonium hydroxide followed by the addition of 10 cc. of nickel sulfatesolution. After standing for 10 minutes, 15 cc. of 1.5% dimethylglyoximeis added while stirring. This solution, after standing for 10 minutes,is filtered to remove excess nickel which has not reacted with theethylenediamine tetra acetic acid. The acid is soluble to a suflicientextent in water for use as a tracing agent. The method of test employedis based on the fact that nickel is selectively sequestered by theethylenediamine tetra acetic acid.

To an aliquot of the filtrate, hydrochloric acid is added to lower thepH to l, and then 10 cc. of 0.25 weight percent solution of potassiumdithio-oxalate is added to give a red color. This color develops becauseof the reaction between the nickel and potassium dithio-oxalate. Theintensity of the color is then measured in a spectrophotometer at a wavelentgh of 508 millimicrons. A calibration curve using distilled watercontaining various concentrations of ethylenediamine tetra acetic acidwas obtained in the foregoing manner. The results of these testspresented in the single figure of the drawing show that theconcentration of ethylenediamine tetra acetic acid plotted against thepercent of light transmittance at a wave length of 508 millimicrons gavea straight-line relationship. This allows the determination of theconcentration of the compound in the water.

In an oil field in which a number of oil wells have been drilled and oilhas been produced from these wells over a number of years there finallyarrives a time when oil no longer flows into the well in sufficientquantity to be recoverable from an economic standpoint. When suchconditions are finally present it is often economically possible toforce a liquid such as water down some of the wells to flood theformation which still contains perhaps of the oil it originallycontained. Depending upon formation structure, such as differences inpermeability caused by fractures or more porous portions, the waterflooding the formation will force oil and other water ahead of it intocertain of the oil wells from which they may be recovered. A greater orless amount of the oil remaining in the formation is thereby recoveredand the percentage that is recoverable depends largely upon the properselection of the water input wells and the amount of water forced intothem. The more that the operator knows about what conditions areunderground the more intelligently he can control the operation and inturn the more oil will be recovered.

At the output wells the oil and water being produced can be separatedand the water tested to determine whether it is connate water or whetherit is input water used in the waterflood if a tracing agent of asatisfactory nature has been placed in the input water used for thewaterflood.

In practicing the present method, the ethylenediamine tetra acetic acidor its water soluble salts is added to the injection water in asutficient quantity to give preferably the concentration of from about 3to about 15 parts per million of the compound in the water. There is nodifficulty in the amount of the compound which may Patented Jan. 13,1959 be used because ethylenediamine tetra acetic acid and its watersoluble salts are not naturally occurring and do not exist naturally inflowing waters whether they be in a stream at the surface. of the earthor flowing underground. Usually 5 parts per million will give desirableresults in water flood operations.

The water is added to the injection water at the input well in a waterflooding operation and production of oil and/or gas or water occurs inthe output wells where the Water produced is separated from the oilproduced and collected at regular intervals from selected wells foranalysis such as by the method indicated but not limited thereto. Thismakes it possible to follow the arrival of the water at the severalproduction Wells from the injection well and allows the operator todetermine whether or not the water is travelling to a particularproduction well.

The present invention is of considerable importance in following theflow of water. Since the ethylenediamine tetra acetic acid and itscompounds are unique in that they do not occur in nature and will not beadsorbed byearth formations and will not be lost if it comes intocontact with earth formations or if it moves through a subsurface earthformation.

The present invention is particularly applicable to water floodingoperations either to initiate recovery of oil and/or gas from asubsurface earth structure or in secondary recovery of oil.

The nature and objects of the present invention having been completelydescribed and illustrated, what I wish to claim as new and useful and tosecure by Letters Patent is:

1. The method of tracing the flow of a stream of water which comprisesadding to said water at a first point a suificient amount within therange of about 3 to about parts per million parts of Water of a compoundselected from the group consisting of ethylenediamine tetra acetic acidand its water soluble salts for detection of said compound, takingsamples of said water at a second point remote from the first point andtesting said samples for the presence of the organic radical of saidcompound whereby the presence of said organic radical indicates thearrival of said water containing said compound at said second point.

2. The method of tracing the flow of water underground which comprisesadding to said water at a first point a suificient amount within therange of about 3 to about 15 parts per million parts of water of acompound selected from the group consisting of ethylenediamine tetraacetic acid and its water soluble salts for detection of said compound,taking samples of said water at 4 a second point remote from said firstpoint after flow of said water underground and testing said samples forthe presence of the organic radical of said compound whereby the flow ofsaid water from said first point underground to said second point isdetermined.

3. A method of tracing the flow of water underground which comprisesadding to said water flowing underground a suflicient amount within therange of about 3 to about 15 parts per million parts of water of acompound selected from the group consisting of ethylenediamine tetraacetic acid and its water soluble salts, taking samples of said water ata second point remote from said first point after the flow of said waterunderground, and testing said samples for the presence of the organicradical of said compound whereby the flow of said water from the firstpoint to the second point is determined.

4. A method of water flooding a field from which hydrocarbons areproduced and tracing the progress of water used in said flooding inwhich water is forced down an input Well to force liquid out of at leastone production well which comprises the steps of adding to said floodingwater a sufficient amount within the range of about 3 to about 15 partsper million parts of water of a compound selected from the groupconsisting of ethylenediamine tetra acetic acid and its water solublesalts taking samples of water from one production well and testing saidsamples of water for the presence of the organic radical of saidcompound whereby the arrival of said flooding water at said productionWell is determined.

5. A method in accordance with claim 4 in which the compound isethylenediamine tetra acetic acid.

6. A method in accordance with claim 4 in which the compound is a sodiumsalt of ethylenediamine tetra acetic acid.

7. A method in accordance with claim 4 in which the amount of thecompound is suflicient to provide approximately 5 parts per million ofthe compound in the flooding water.

References Cited in the file of this patent UNITED STATES PATENTS2,578,500 Bernard et al Dec. 11, 1951 2,589,219 Bond et al Mar 18, 19522,660,887 Frei Dec. 1, 1953 2,696,468 Fisher Dec. 7, 1954 OTHERREFERENCES Martell: Chem. of the Metal Chelate Comp, page i

1. THE METHOD OF TRACING THE FLOW OF A STREAM OF WATER WHICH COMPRISESADDING TO SAID WATER AT A FIRST POINT A SUFFICIENT AMOUNT WITHIN THERANGE OF ABOUT 3 TO ABOUT 15 PARTS PER MILLION PARTS OF WATER OF ACOMPOUND SELECTED FROM THE GROUP CONSISTING OF ETHYLENEDIAMINE TETRAACETIC ACID AND ITS WATER SOLUBLE SALTS FOR DETECTION OF SAID COMPOUND,TAKING SAMPLES OF SAID WATER AT A SECOND POINT REMOTE FROM THE FIRSTPOINT AND TESTING SAID SAMPLES FOR THE PRESENCE OF THE ORGANIC RADICALOF SAID COMPOUND WHEREBY THE PRESENCE OF SAID ORGANIC RADICAL INDICATESTHE ARRIVAL OF SAID WATER CONTAINING SAID COMPOUND AT SAID SECOND POINT.